The incident began about 6:30 p.m. when police were alerted about a stolen 2007 Chevy pickup heading south on Interstate 15. The driver, at speeds approaching 100 mph, tried to outrun police, driving on I-15, several surface streets, and then Interstate 5, police said.

As the truck approached the San Ysidro border crossing to Mexico, it got stuck in traffic.

The officer and the agent approached on foot but the driver rammed two San Diego police vehicles and a Border Patrol vehicle as he tried to make a U-turn and drive north on a southbound lane of I-5, police said.

"Fearing they were going to be seriously injured," the officer and agent opened fire, said Lt. Jorge Duran.

The San Diego police officer has been with the department for six years; the Border Patrol agent with the agency for seven years, authorities said.